Journal of Research of the National Bureau of Standards
AbstractThe radio refractive index of air is a function of atmospheric pressure, temperature, and humidity and is found to vary in a systematic fashion with climate. It was found that the surface value of the refractive index may be estimated four to five times more accurately from charts of reduced-to-sea-level values than from similar sized charts of surface index. Worldwide maps of 5-year means of this reduced value are presented for the months of February and August, for the minimum monthly mean value of the year and for the range of monthly mean values. Year-to-year variation of monthly means is also considered. Applications of these data to the prediction of radio field strengths indicate a possible 30-decibel difference in median level of identically equipped tropospheric communications systems due to climate alone.
CiteJ. Res. Nat. Bur. Stand., Sec. D, Radio Prop., Vol. 63D, No. 3, p. 259
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